Let me provide some examples to paint the picture of what i mean. Finding someone with your same name can give you a feeling that you must be similar to the other individual. However, a name sheds very little light on the nature of someone's character or interests. Discovering that you have the same birthday can also give a subconscious impression that perhaps this is your long-lost twin, you feel that such an occurrence is a rare treasure, but countless people are born on the same day every year, so it isn't all that rare at all.
The more profound connections we seek and get excited about, however, are those of interests and beliefs. Discovering you have read the same book, are mesmerized by the same album by the same band, or are made speechless by the works of the same artist have a tendency to breed friendship, at least to a small degree. Discovering that you have similar views on religion and faith is perhaps the connection i celebrate the most, but perhaps this is the element that is most core to my being...so that could be sharing in common politics or philosophies for others. Once one connection is unearthed, you seek others. You end up exchanging interests in the process of trying to find those you hold in common.
The reason i have been pondering all this is because i have noted in myself that I always search out for commonalities when i meet someone new or speak with an old friends. I feel inspired by the passions of others, whether they are shared by me or not. Once a commonality is discovered, i get sort of swept away in the enthusiasm of it, or rather in the enthusiasm of furthering my web of connection with others. I think this is how we were designed by our Creator. He longs for connections with us, and since we are made in His image, we long deeply for connections with others.